First, we segregate DED into either aqueous deficiency (too little moisture production), evaporative dry eye disease (poor tear quality with its hallmark of Meibomian Gland Dysfunction – MGD), or a combination of the two. This is done with a series of tests and a complete dry eye exam.
We like to use the analogy of a “sprinkler system” (the accessory lacrimal glands) managing minute-by-minute moisture on the eye, where the components are a complex mixture of water, salt, protein, and oil – kind of like a clear salad dressing. As in salad dressing, oil and water don’t mix – so the oil, floating on the surface of the tear film, helps to seal that moisture in and makes the tears more “stable” – in that the water can’t leave – almost as though there is a liquid plastic wrap on the surface of the eye. The “fire hose” produces only saltwater and tends to send in a flood. This is described in more detail below.
It is important to distinguish this type of exam – which may not be covered at least in part by insurance companies – from the routine medical eye exam, in which a full range of medical eye diseases are screened for – an exam commonly covered by most insurance companies, but is not specific enough for this very focused evaluation utilizing this advanced technology.
In cases where the eye is deficient in oil, the “salad dressing” evaporates too easily and can trigger the “fire hose.” This “fire hose” is a large (lacrimal) gland responsible as an emergency back-up to the sprinkler system and is the gland we cry with if we get emotional or have something get into our eye. When the sprinkler system lets us down in any way, the fire hose will frequently be triggered – resulting in the overflow of salty tears that cause our eyes to tear up and frequently to sting or burn (the effect of putting salt into a dry, sore eye). This is referred to as “reflex tearing” – when the irritation triggers the eye to cry